1. Field of the Invention
This invention relates to improvements in braking apparatus and more particularly, but not by way of limitation, to a parking brake for large off-highway vehicles.
2. Description of the Prior Art
Exceedingly large off-highway vehicles are in widespread use today, particularly in the mining industry wherein it is advantageous to haul great quanitities of ore in a single transport vehicle. Many of these vehicles are powered by wheel mounted electric motors, and the great weight of the vehicle coupled with the great size thereof creates problems in the braking apparatus that may not be present in vehicles of a more conventional size. In addition, it is extremely important that the braking of these vehicles be efficient since any loss of braking power can result in great damage to both the vehicle and any personnel which might be in the vicinity of the vehicle. Of course, it is common practice to provide parking brakes for these vehicles in addition to the other braking apparatus on the vehicle. There are many parking devices which have been developed for off-highway vehicles such as shown in the Friedman patent No. 2,775,319, issued Dec. 25, 1956, and entitled "Spring Applied Wheel Brake;" Lech, Jr. et al U.S. Pat. No. 3,893,556, issued July 8, 1975, and entitled "Fluid Released Clutch;" Yamamoto et al U.S. Pat. No. 4,014,414, issued Mar. 29 1977, and entitled "Power Parking Failsafe Disc Brake;" Hanks U.S. Pat. No. 4,078,637, issued Mar. 14, 1978, and entitled "Fluid Disengaged and Spring Urged Brake;" and the Hedgcock U.S. Pat. No. 4,129,204, issued Dec. 12, 1978, and entitled "Spring Operated Clutch with Small and Large Bolts." One particular disadvantage of the presently available parking brakes for large off-highway vehicles, such as shown in the aforementioned patents, is the fact that an operator of the vehicle may inadvertently forget to "set" the parking brake when he leaves the vehicle. This is a particular problem in large vehicles of this type because of the overall weight involved. For example, when one of these vehicles has been parked at the edge of a precipice, such as the edge of an open pit mining operation, the omission of the setting of the parking brake may result in the accidental movement of the vehicle downwardly over the edge of the precipice, not only causing great damage to the vehicle itself, but also creating a hazard for any operating personnel in the vicinity of the accident.